The satisfactory removal of greasy soils/stains, that is soils/stains having a high proportion of triglycerides or fatty acids, is a challenge faced by the formulator of detergent compositions for use in machine laundry and dishwashing methods. Surfactant components have traditionally been employed in detergent products to facilitate the removal of such greasy soils/stains.
In particular, surfactant systems comprising cationic ester surfactants have been described for use in greasy soil/stain removal. By cationic ester surfactants it is meant those compounds having surfactant properties which comprise at least one ester (i.e. --COO--) linkage and at least one cationically charged group. The cationically charged group is often an ammonium or substituted ammonium group.
For example, EP-B-21,491 discloses detergent compositions containing a nonionic/cationic surfactant mixture and a builder mixture comprising aluminosilicate and polycarboxylate builder. The cationic surfactant may be a cationic ester. Improved particulate and greasy/oily soil removal is described.
U.S. Pat. No. 4,228,042 discloses biodegradable cationic surfactants, including cationic ester surfactants for use in detergent compositions to provide greasy/oily soil removal. The combination of these cationic surfactants with nonionic surfactants in compositions designed for particulate soil removal is also described. Anionic surfactants are disclosed as optional components of the compositions, but are present at low levels relative to the cationic surfactant component.
U.S. Pat. No. 4,239,660 discloses laundry detergent compositions containing cationic ester surfactant and nonionic surfactant at defined weight ratios and an alkalinity source. The alkalinity source enables a wash solution having a pH of from 8 to 10 to be formed within 3 minutes of dissolution of the composition in water at 100.degree. F. (37.degree. C.) at a solution concentration of 0.15%.
U.S. Pat. No. 4,260,529 discloses laundry detergent compositions having a pH of no greater than 11 containing cationic ester surfactant and nonionic surfactant at defined weight ratios. Anionic surfactants are disclosed as optional components of the compositions, but are present at low levels relative to the cationic ester surfactant component.
The Applicants have now found that certain cationic ester surfactants, in which the cationically charged group is an ammonium group substituted by at least one hydroxyalkyl group, demonstrate enhanced stain removal performance under the wash conditions of a typical laundry method, particularly at low wash temperatures. The enhanced low wash temperature performance is believed to be related to the good cold water solubility of these cationic esters. Additionally, the cationic ester surfactants demonstrate enhanced perfume robustness, that is to say that fabrics washed in perfume-containing detergents containing these surfactants have an improved perfume profile.
The prior art documents cited above include a general description of cationic ester surfactants in which it is envisaged that the cationically charged group is an ammonium substituted optionally by various substitutuent groups. Choline ester surfactants having methyl substituents are however, exclusively exemplified. None of the documents provides any teaching of the enhanced stain removal capability or perfume robustness exhibited by the present cationic ester surfactants in which the cationically charged group is an ammonium group substituted by at least one hydroxyalkyl group.
All documents cited in the present description are, in relevant part, incorporated herein by reference.